This invention relates to static screen separators and particularly to improvements in such apparatus effecting space savings and increased operating efficiency.
In the prior art, an inclined screen is supplied with a liquid-solids slurry either in a direct, full flow discharge upon the screen or in an overflow from an adjacent head box. An example of the former may be found in the U.S. Pat. No. 3,353,674, to Leeman dated Nov. 21, 1967. Separators of the Leeman type have certain disadvantages, particularly in the turbulence produced on the screen surface. Leeman provides a flexible movable wall to control flow onto the screen surface but, as will be obvious, the movable wall functions primarily as a flow deflector, being positioned immediately in the path of discharge upon the screen.
An example of a head box construction is found in U.S. Pat. No. 3,452,876, to Ginaven, dated July 1, 1969. The device disclosed in the Ginaven patent has enjoyed and continues to enjoy great commercial success in a number of material processing arts. It locates a head box to the rear of the upper end of an inclining screen, the head box being continuously supplied with a pulp or like slurry the components of which are to be separated and/or classified. Rising slurry in the head box overflows a weir and in sheet-like form moves smoothly down the upper screen surface. Liquid and fine solids pass through screen apertures and are appropriately collected and carried off. Coarse solids descend in a rolling, sliding action along the screen surface and discharge over a lower end thereof. The Ginaven device while eminently successful, as noted, does have certain limitations resulting from the rear location of its head box. Floor space required for a unitary assembly comprising a screen unit and a head box is greater than would be required for a screen unit alone. Also, increases in flow rate, productive of higher flow velocities, may not be fully contained and so lead to lowered separation efficiency.
The U.S. Pat. No. 3,833,123, to Walker, dated Sept. 3, 1974, shows a screen separator with a differently positioned head box. In this instance, the head box is mounted above the screen structure and over the frame enclosure for the screen unit. Serious construction as well as space problems of a different kind result with this arrangement. Also, in this case the overflowing slurry reaches the screen surface with an impact that causes turbulence and reduces separating efficiency.
Other prior art patents evidence various head box arrangements, the most pertinent of which are U.S. Pat. Nos. 3,363,769 and 3,794,164. U.S. Design Pat. Nos. 226,398 and 229,055 are similarly pertinent. However, none of these patents anticipate the specific improvements of construction or embody the advantages of the present invention.